Knowra Diffuse sky radiation Diffuse sky radiation Diffuse sky radiation is sunlight scattered by atmospheric molecules, aerosols, and clouds that reaches a surface from directions across the sky rather than directly from the Sun.
Rayleigh scattering : The scattering of light by particles much smaller than its wavelength, especially gas molecules in the atmosphere. Air molecules scatter shorter wavelengths strongly, creating much of the blue diffuse light in a clear sky.
Global horizontal irradiance : The total solar irradiance received by a horizontal surface, combining direct and diffuse components. It adds diffuse sky radiation to the direct sunlight projected onto a horizontal plane.
Direct solar radiation : Solar radiation that reaches a surface along the unobstructed direction from the Sun's apparent disk. It is the beam component excluded from diffuse sky radiation.
Irradiance : Radiant power incident on a surface per unit area. Diffuse sky radiation is an irradiance component defined by the directions from which light arrives.
Blue sky : The blue appearance of a clear daytime sky, caused mainly by wavelength-dependent scattering of sunlight by air molecules. It is a familiar visible result of molecular scattering that also supplies diffuse illumination.
Mie scattering : The scattering of light by particles comparable in size to its wavelength, including many atmospheric aerosols and cloud droplets. Aerosols and droplets redirect sunlight across the sky, often producing brighter, less blue diffuse illumination.
Diffuse horizontal irradiance : The solar irradiance received by a horizontal surface from the sky, excluding the direct solar beam. This measurement isolates the diffuse component on a horizontal surface.
Global solar radiation : The total solar radiation received at a surface, including direct and diffuse contributions. This broader quantity combines diffuse sky radiation with direct solar radiation.
Radiance : Radiant power traveling in a specified direction per unit projected area and solid angle. The sky's directional radiance describes the angular pattern whose contributions form surface irradiance.
Overcast sky : A sky covered extensively by clouds, with little or no direct sunlight reaching the ground. Clouds scatter sunlight broadly, making diffuse radiation dominate surface illumination.
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